net/Space: delete orphaned externs from deleted drivers

The drivers associated with the prototypes in this commit have
been deleted some time ago, but the externs escaped detection.
Using a simple "git grep" shows that these references are
historical artefacts, only mentioned by the deleted lines.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>